As is more fully explained in co-pending application Ser. No. 07/348,627, normal food intake which is known to lead to gastric acid secretion because of stomach distension and because of the action of only a few commonly ingested food constituents such as caffeine, calcium ions, alcohol, and the digestion products of protein.
Early attempts in the food art to produce a "stomach friendly" coffee, that is a coffee which will produce less or no heartburn in susceptible individuals, centered upon the deacidification of coffee such as by chemically neutralizing the acids present in coffee by the addition of a food-grade alkaline agent.
Farr and Horman (U.S. Pat. Nos. 4,160,042 and 4,204,004) teach a method of reducing the caffeine and/or chlorogenic acid content of coffee by treatment with particles of carob pods which absorb the caffeine and chlorogenic acid. Magnolato (U.S. Pat. No. 4,278,696) teaches a process for deacidifying a coffee extract by contacting it with chitosan in divided form and recovering the resultant deacidified extract. This patent stresses the importance of the removal of chlorogenic acid since it is the predominant acid found in coffee. However, other acids including malic acid are also reduced by the treatment. Another process, described in U.S. Pat. No. 4,317,841 to Brambella and Horman, teaches reduction in the acidity of a coffee extract by electrodialysis. The non-cathodic extract is collected, contacted with subdivided chitosan and, after removal of the chitosan, is mixed with at least a part of cathodic extract to provide a deacidified coffee extract.
Published Patent Application DE 3,239,219, published Apr. 26, 1984, discloses contacting an aqueous extract of green coffee beans with an anion-exchange resin, the resin having been loaded by adsorption with at least one nonacidic coffee extract constituent in order to exchange the acids present in the aqueous extract to produce a reduced chlorogenic acid green coffee. The object is to produce a coffee product which would reduce irritation of stomach mucosa and not cause stomach acidity.
PCT International Publication Number WO 87/04598 having a publication date of Aug. 13, 1987 teaches a coffee product with an increased chlorogenic acid content. This elevated chlorogenic acid level is said to improve the digestibility of coffee by reducing human acid secretion. The physiology studies reported in the patent application were performed on human male and female subjects. However, the poor methodology utilized in the studies including the lack of proper scientific controls render the results questionable at best.
Co-pending application Ser. No. 07/348,627 discloses production of a stomach friendly coffee by selectively removing malic acid and without sacrificing the large percentage yield loss and flavor penalty which results from the removal of a majority of chlorogenic acid as taught by prior art references.
It is an object of the present invention to provide a method for removing malic acid from coffee. It is a further object of the invention to provide a method of removing malic acid from coffee which method includes malolactic fermentation of an aqueous coffee extract.